In a manufacturing process of a semiconductor device or an FPD (Flat Panel Display), a plasma is used for performing a microprocessing or a treatment such as etching, deposition, oxidation, sputtering or the like so that a reaction of a processing gas can be carried out under a relatively low temperature. In general, a plasma generation technique of a plasma processing apparatus is classified into two types: one using glow discharge or high frequency power and the other using microwaves.
As disclosed in Japanese Patent Laid-open Application No. H6-283474 and U.S. Pat. No. 5,494,522, for example, the high frequency discharge plasma processing apparatus applies a high frequency power for plasma generation to an upper electrode or a lower electrode via a matching unit, the upper and the lower electrode being disposed in parallel in an evacuable processing chamber or a reaction chamber, the lower electrode having thereon a target substrate (semiconductor wafer, glass substrate or the like). Next, electrons are accelerated by a high frequency electric field generated by the high frequency power, and ionization by collision between the electrons and the processing gas generates a plasma. Then, radicals or ions in the plasma are consumed in performing a desired microprocessing (e.g., an etching processing) on a surface of the substrate.
Recently, along with the trend for a miniaturization of a design rule in a manufacturing process, a high density plasma in a low pressure is required for a plasma processing. The aforementioned high frequency discharge plasma processing apparatus employs a high frequency power of a frequency band (higher than or equal to 40 MHz) much higher than a conventional frequency band (13.56 MHz). However, if a frequency of a high frequency discharge increases, the high frequency power applied from a high frequency power supply to a rear surface or a backside of an electrode via a power feeder flows toward a main surface of the electrode (surface facing a plasma) along the surface of the electrode by skin effects. Next, a high frequency current flows from each portion on the main surface of the electrode toward the plasma. In a conventional plasma processing apparatus, a single power feeder is connected with a central portion of the rear surface of the electrode, so that a singularity is provided at a central portion of the main surface of the electrode which is farthest away from the power feeder. Therefore, a discharge current in the central portion of the main surface of the electrode (high frequency current flowing toward the plasma) becomes greater than that in an edge portion thereof and, hence, a plasma density becomes higher in the central portion than in the edge portion. As a result, process characteristics become radially non-uniform.